I am setting up the homepage to display six images as sort of full screen menu items that when clicked on, will navigate the user to other pages.

At the bottom of each image is a caption that describes the menu selection for that image.

Due to different device’s screen sizes if I set the image preview height and width to the same value (so the images will appear square), the chances are that vertical scrolling up will be needed to see the bottom of the second row of images (so the user can see the captions located on the bottom of the images).

I would like the user to be able to see all six captions without having to scroll to see the bottom row of images. So I found out that I can set the “image height” to a lower value so the images will be shorter vertically (rectangle not square anymore), allowing all six images to fix on my devices display and allow me to see all six captions without having to scroll.

Unfortunately, if I switch to a different device, I will either end up with having to scroll up because the second row is still too low on the other device, or I end up with a ton of whitespace when displayed on a large-screen device like a desktop pc.

So, is there some way to configure your photo gallery to auto-calculate the height size of the preview images so they will fit perfectly on any device without the user having to scroll vertically?

My bad – I forgot to mention that I am already using the fixed column mode.

Your plug in will automatically rearrange the items based on the device screen size, but it only bases this on the devices width. I was hoping that it would also consider the available height for the images, so if all the images won’t fit vertically (without scrolling down) it will automatically reduce the “image height” setting so that all the images will fit, even if the images are no longer square.

Unfortunately there is no option to make gallery work as you described.
But you can try Fixed type of gallery, where you can set strict images size – both height and width.
Also you can try Horizontal type of gallery wich also has an option to control it height.
So you can put required image heigh and scroll images on mobile screens.